Activators for the polymerization of pyrroldione



Patented May 34, 10655 This invention relates to a new process forpolymerizing pyrrolidone. More particularly, the invention is concernedwith a new polymerization procedure for the manufacture of pyrrolidonepolymers, wherein new catalyst-activator systems are employed.

Pyrrolidone is normally polymerized in the presence of a polymerizationcatalyst, such as the alkali metals and various organic metalliccompounds, as well as sodium amide, calcium oxides and hydroxides, andthe like. It has been found that the activity of these catalysts duringthe polymerization reaction can be enhanced by the addition thereto ofvarious compounds which are classed as polymerization activators. Forexample, among the compounds heretofore proposed as polymerizationactivators, there may be named the acyl compounds, such as acetylpyrrolidone, acetyl morpholone, benzoyl chloride and the like; lactones,such as gamma butyrolactone, and the like; alkyl esters of monoanddicarboxylic acids, such as ethyl acetate, ethyl oxalate, and the like;and the esters of polyhydric alcohols, such as ethylene glycoldiacetate, and the like. However, the presently known catalyst-activatorsys tems for the polymerization of pyrrolidone leave much to be desired.

Many of the compounds heretofore proposed as polymerization activatorsfor pyrrolidone polymerization are CllffiCtllll to handle, whichobviously makes them undesira ble from a commercial standpoint.Furthermore, many of the prior art compounds proposed as activators tendto affect the polymers as they are formed, resulting in undesirablecol-or and detrimental changes in physical properties of the polymers.In addition, many of the prior art compounds introduce end groups intothe polymer chains which decrease the dye receptivity thereof. Moreover,many of the prior art activators result in the production of polymershaving relatively low specific viscosities. Shaped articles, such asfibers for example, formed from such polymers are weak and cannot bedrawn to any given degree. Accordingly, there has been a need in the artfor a catalyst-activator system which overcomes the above disadvantagesand which is easily and readily adaptable to a commercial operation.

It is the principal object of the present invention to provide newcatalystnctivator systems for the polymerization of pyrrolidone. It isanother object of the invention to provide new catalyst-activatorsystems for the polymerization of pyrrolidone which result in theformation of polymers having desirable improved physical properties,such as good solubility, excellent color and high molecular weight. Itis another object of the invention to provide new catalyst-activatorsystems for the polymerization of pyrrolidone which result in theformation of polymers having greatly improved dyeaoility. it is afurther object or the invention to provide a new process for preparingpyrrolidone polymers. Other objects and advantages of the invention willbe apparent from the description thereof hereinafter.

In general, objects of the invention are accomplished by polymerizingmonomeric pyrrolidone under polymerization conditions in the presence ofa polymerization catalyst and activating the polymerization with atrihalide of aluminum, bismuth and antimony, a tctrahalide of tin,

titanium, zirconium and lead, or the pentahalide of antimony.

The tri-, tetraand pentahalides of the elements mentioned above suitablefor use in the practice of this invention include aluminum trichlori-de,aluminum tribromide, aluminum triiodide, stannic tetrachloride, stannictetrabromide, stannic tetraiodide, titanium tetrachloride, titaniumtetrabromide, lead tetrachloride, zirconium tetrachloride, bismuthtrichloride, bismuth tribromide, antimony trichloride, antimonytribromide, antimony triiodide, antimony pentachloride, antimonypentaiodide, antimony pentafluoride and the like.

The polymerization activators can be employed with any of the knowncatalysts normally used in the polymerization of monomeric pyrrolidone.Among the catalysts for polymerizing pyrrolidone which are useful in thepractice of the present invention are the alkali metals, that is,sodium, potassium, and lithium; the hydrides, hydroxides, oxides, andsalts of the alkali metals, that is, such salts as sodium, potassium,and lithium pyrrolidone; organic metallic compounds, preferably thosewhich are strongly basic, for example, the lithium, potassium, andsodium alkyls and a-ryls of the alkali metals, such as sodium phenyl andthe like; sodium amide, and other cataylsts.

Preparation of polypyrrolidone with the activators of this invention maybe carried out with varying amounts of components. In general, thechemical equivalent amount of catalyst must exceed by at least a slightexcess the number of chemical equivalents of activator. The catalyst maybe employed in a range of 0.002 to 0.25 chemical equivalents of catalystbased upon one mole of monomeric p-yrrolidone. It is preferred, however,that the catalyst be employed in a range of 0.005 to 0.25 chemicalequivalents of catalyst based upon one mole of monomeric pyrrolidone.The activator is employed in a range of 0.0001 to 0.075 chemicalequivalents of activator based upon one mole of monomeric pyrrolidone.Preferably, however, the activator is employed in a range of 0.001 to0.075 chemical equivalents of activator based upon one mole of monomericpyrrolidone. Thus, for activators containing more than one potentiallyreactive substituent on the salts named hereinabove, the maximum numberof moles of activator that can be employed for a given number of molesof catalyst must be considerably less than the number of moles ofcatalyst. For example, where one mole of aluminum tric'nloride, threechemical equivalents, is employed in carrying out the polymerization, aslight excess of three moles, three chemical equivalents, of catalyst isrequired.

T polymerization reaction of this invention is carried out attemperatures Within a range of 70 C. to C. in the preferred practice ofthe invention, however, the polymerization reaction is carried out at atemperature in the range of 20 C. to 70 C. The reaction time will varywiih the temperature and the amount of monomer employed. Where highertemperatures are used in the polymcrization reaction, the total timerequired to complete polymerization is shorter. The polymerizationperiod is also greatly affected by the particular catalyst-activatorsystem employed. Generally, in carrying out a polymerization reactionaccording to the present invention, the monomer, catalyst, and activatorare placed in a polymerization vessel and subjected to polymerizationtemperatures as hereinabove defined. However, the steps necessary toobtain complete polymerization will vary, depending upon the type ofcatalyst which is employed. For example, many of the catalysts, such aspotassium hydroxide, cause the formation of water durin thepolymerization reaction.

Tl.e presence of such water has a deleterious ettect upon thepolymerization reaction, namely, it hinders further polymerization andeven brings the same to a halt in many instances. Accordingly, in orderto achieve the desired results, it is necessary to remove such water ofreaction from the reaction medium. This can easily be accomplished by asimple vacuum distillation. Therefore, when employing a catalyst, suchas sodium hydroxide, the monomeric pyrrolidone is placed in thepolymerization vessel and the catalyst added thereto. The reactants arethen subjected to vacuum distillation and mechanical stirring in orderto remove the water formed. Although mechanical stirring is notabsolutely necessary, it greatly aids in removal of the water. When allof the water in the reaction vessel is completely removed, the activatoris then added to the retction mixture and the reaction continued. Whenan alkali hydride is employed as the catalyst, all of the reactants maybe added to the polymerization vessel simultaneously, and thereafter thereaction carried through to completion. However, it is preferred to addthe alkali hydride to the monomer in the reaction vessel and then removethe hydrogen thus generated prior to the addition of the activator tothe reaction mass. This procedure eliminates all danger of any possibleexplosive results due to the presence of hydrogen in the reactionvessel. An advantage in the use of an alkali hydride over thewater-forming catalyst, such as potassium hydroxide, is the eliminationof the distillation step necessary for the removal of the water ofreaction, since with hydrides a pyrrolidone salt and gaseous hydro genare formed.

The instant method for polymerizing pyrrolidone may be carried out byeither solution, emulsion, suspension or bulk polymerization techniques.The solution and emulsion polymerizations may be either batch orcontinuous methods. When solution polymerization is employed, themonomeric pyrrolidone is dissolved in a solvent such as 1,4-dioxane. Thedesired catalyst and activator are added to the solution and thepolymerization is carried out under the proper conditions. Well-knownsolution polymerization apparatus is suitable for carrying out themethods employed in the practice of this invention. When applyingemulsion or suspension polymerization procedures to the preparation ofpolypyrrolidone with the activators of the invention, the monomercontaining the catalyst is dispersed in a known solvent therefor, suchas petroleum ether, con taining an emulsifying agent. Subsequently, thedesired activator is added to the dispersion and the reaction mixture issubjected to polymerization condit ons. A suitable coagulant is thenadded to the polymerized mixture in order to precipitate the polymer. Asuitable emulsifying agent which may be employed is sodium laurylsulfate, and a suitable coagulant is phosphoric acid.

While it is not positively known exactly what takes place whenpyrrolidone is polymerized in accordance with the present invention, itis believed that the polymerization is accomplished by first formingionic pyrrolidone salts. For example, when one employs potassiumhydroxide as a catalyst, a reversible reaction takes place between themonomeric pyrrolidone molecules and the hydroxide ion, with thesubsequent formation of water. Since this reaction is reversible, it isnecessary that the water be removed in order to carry outpolymerization. Formation of the pyrrolidone anion results in anelectron distribution which is nucicophilic. In order for chainpropagation to take place, the nucieophilic ion attaches to apyrrolidone ring which has been activated by an activator molecule,thereby causing a weak bond in the ring between the nitro gen and thecarbonyl group, and causing th ring to open. forming a ewly activatedposition and an anion on the polymer chain. A proton (hydrogen ion) froma monomeric pyrrolidone transfers to the chain anion resulting in ametal-nitrogen linkage and the regeneration of n nucleophillcpyrrolidone anion to further catalyze the reaction. The catalyst iscontinuously consumed and generated throughout the entire reaction bythe transfer of a proton (hydrogen ion) giving rise to the formation ofthe pyrrolidone anion. It is believed that the function of an activatoris to activate the pyrrolidone monomer by displacing the hydrogen on thenitrogen atom of the pyrrolidone ring, thereby causing an electrophilicstate within the monomeric 'pyrrolitlone molecule, such that the bondbetween the nitrogen atom and the carbonyl grou of the ring is brokenwhen such molecule is attacked by a pyrrolidone anion, thereby forming astraight chain. Such chain is attached to a pyrrolidone ring by bondingto the nitrogen atom therein. The ring structure is in turn opened bythe attack of a nucleophilic pyrrolidone ion formed by the transter of aproton from a monomeric pyrrolidonc molecule to a chain nitrogen.Irrespective of whether or not the above theory is correct, the use ofthe activators defined herein, to activate the polymerization ofpyrrolidone, has produced unexpectedly good results. For example, as maybe seen from the data in the following examples, there is a distinctivedifference in the strength of the metal-nitrogen bonds and thebenzamicle bonds. On washing, a large portion of the former, that i themetalnitrogen bonds, are hydrolyzed, whereas the latter are not. Thishydrolysis of the metal-nitrogen bonds results in the formation of amineend groups on the polymer. Consequently, as one would expect, there is agreat increase in dyeability with acid dyes of polypyrrolidone pre paredwith the activators of this invention in comparison to polypyrrolidoneactivated by the known carbonyl activators, such as benzoyl chloride,the latter leading to stable amide linkages. Emission spectrographicstudies of the washed versus the unwashed polymers showed that the metalatoms were largely removed by the simple washing procedure. On the otherhand, ultraviolet studies of the benzamide end groups of unwashed versuswashed benzoyl chloride activated polypyrrolidone showed no evidence ofany loss by hydrolysis of these end groups on washing.

Polypyrrolidone prepared with the activators of this invention has amelting point of about 260 C. and is soluble in formic acid, mixtures offormic acid and water, and all of the known solvents forpolypyrrolidone. It is particularly adapted for use in the manufactureof shaped articles, such as filaments, fibers, films, rods, bristles andthe like. Lower molecular weight polymers prepared in the same mannermay be employed in the manufacture of coatings or lacquers.

Where the polypyrrolitlone is to be employed in the formation offilaments, fibers, and the like, there are various methods known forfilament and fiber formation. These methods include the melt spinning,dry spinning and wet spinning methods. Where the wet spinning method isemployed, the polymer is dissolved in a suitable solvent andsubsequently spun from the solution into a coagulating bath. In the dryspinning method, the polymer is dissolved in a volatile solvent andextruded into a heated atmosphere in order to remove the solvent. Themelt spinning method involves melting the polymer under temperature andpressure and extruding the melt through a spinneret into the atmosphere.

Shaped articles which have a modified appearance or modified propertiesmay be prepared from the polypyrrolidone whose polymerization has beenactivated by the activators of the instant invention. Various reagentsto accomplish the desired ellect include plasticizers, pigments, dyes,antistatic agents, fire-retarding agents and the like.

The following examples are intended to illustrate the invention morefully but are not intended to limit the scope thereof, for it ispossible to etlcct many modifications therein. In the examples, allparts and percents are by weight unless otherwise indicated.

EXAMPLE I To a 25 gram (0.294 mole) sample of essentially anhydrouspyrrolidone, there was added under a nitrogen atmosphere 0.7.5 gram(0.0315 mole) of sodium hydride catalyst. When the evolution of hydrogengas was completed, 0.78 gram (0.00298 mole) of stannic chloride wasadded to the reaction mixture. This mixture was stoppered to protect itagainst the atmosphere and was permitted to stand for 25 hours at about25 C. The polymer was recovered by breaking up the cal; grinding it in aWiley mill, and washing the powder first with water, then with acetonein a Waring Blender. The polymer was subsequently air-dried to constantweight. There was a yield of 12.0 grams or 49 percent of polymerrecovered. The polymer had a specific viscosity, determined on 0.5percent solutions of the polymer in 90 percent formic acid, of 4.372. Acontrol sample prepared under the same conditions with monomer from thesame batch but in the presence of 0.41 gram (0.00292 mole) of benzoylchloride, an acyl activator, resulted in 6.9 grams or a 66 percent yieldof polymer recovered, based on 10.4 grams of the polymer cake that wasworked up. The benzoyl chloride activated polymer had a specificviscosity of only 1.375, determined in the same manner as the stannicchloride activated polymer. The comparative results are set torth in thetable below.

*Based on 10.4 grams of the polymer cake worked up.

EXAMPLE H To a 25 gram (0.294 mole) sample of essentially anhydrouspyrrolidone, there was added under a nitrogen atmosphere, 0.75 gram(0.0315 mole) of sodium hydride catalyst. When the evolution of hydrogengas was completed, 0.39 gram (0.00293 mole) of anhydrous aluminumchloride was added to the reaction mixture. This mixture was stopperedto protect it against the atmosphere and permitted to stand for 25 hoursat about 25 C. The polymcr was recovered by breaking up the cake,grinding it in a Wiley mill, and washing the powder first with water,then with acetone in a Waring Blender. There was recovered 19.3 grams ora 77 percent yield. The polymer had a specific viscosity, determined on0.5 percent solutions of the polymer in 90 percent formic acid, of3.914. A control sample prepared under the same conditions with monomerfrom the same batch but in the presence of 0.41 gram (0.00292 mole) ofbenzoyl chloride, an acyl activator, resulted in a yield of 6.9 grams or66 percent of recovered polymer, based on 10.4 grams of the polymer cakethat was worked up. The benzoyl chloride activated polymer had aspecific viscosity of only 1.375, determined in the same manner as thatof the aluminum chloride activated polymer. The comparative results areset forth in the table below.

Grams Weight of Percent ns at Activator Used Ml. Polymer Yield 0.5%conc.

Recovered in HCOOH Bcnzoyl chloridc 0. 41 0. 84 *6. 9 6 1. 875 Aluminumchloride (anhydrous) 0. 39 19. 3 77 3. 914

*Based on 10.4 grams of the polymer cake worked up.

EXAMPLE H1 it in a Wiley mill, and washing the powder first with water,then with acetone, in a Waring Blendor. The polymer was subsequentlyair-dried to constant weight. There was recovered a yield of 17.5 gramsor percent. The polymer had a specific viscosity, determined on 0.5percent solutions of the polymer in 90 percent formic acid, of 3.024. Acontrol sample prepared using monomer from the same batch under the sameconditions, but with 0.41 gram (0.00292 mole) of benzoyl chloride, anacyl activator, resulted in 6.9 grams or a 66 percent yield of recoveredpolymer, based on 10.4 grams of the polymer cake worked up. The benzoylchloride activated polymer had a specific viscosity of only 1.375,determined in the same manner as that of the antimony pentachlorideactivated polymer. The comparative results are set forth in thefollowing table.

*Based on 10.4 grams of the polymer cake worked up.

EXAMPLE IV To a 25 gram (0.294 mole) sample of essentially anhydrouspyrrolidone, there was added under a nitrogen atmosphere 0.75 gram(0.0315 mole) of sodium hydride catalyst. When the evolution of hydrogengas was completed, 0.56 gram (0.00295 mole) of titanium tetrachloridewas added to the reaction mixture. This mixture was stoppered to protectit against the atmosphere and permitted to stand for 25 hours at about25 C. The polymer was recovered by breaking up the cake, grinding it ina Wiley mill, and washing the powder first with water, then withacetone, in a Waring Blendor. The polymer was su sequently a irdried toconstant weight. There was recovered 19.2 grams or a 77 percent yield ofpolymer. The polymer had a specific viscosity, determined on 0.5 percentsolutions of the polymer in 90 percent formic acid, of 0.761.

EXAMPLE V To 62.5 grams of essentially anhydrous pyrrolidone from thesame batch as used in the previous examples, there was added under anitrogen atmosphere 4.17 grams of percent potassium hydroxide,equivalent to 3.54 grams or 0.063 mole of pure potassium hydroxide. Then12.5 grams of the mixture were distilled off at 100 C. and 0.8 mm. ofmercury leaving approximately 50.0 grams of pyrrolidone, of which 0.063mole was present as the potassium salt.

The 50.0 grams of pyrrolidone was divided into two equal parts, eachcontaining 0.0315 mole of the potassium salt. To one portion there wasadded 0.37 ml. (0.878 gram or 0.00294 mole) of antimony pentachloride.The reaction mixture was permitted to sit for approximately 24 hours at25 C. The polymer was recovered by breaking up the cake, grinding it ina Wiley mill, and washing the resultant powder first with water, andthen with acetone, in a Waring Blendor. Following each wash the polymerwas filtered. After washing was completed the polymer was air-dried andweighed. There was recovered 8.2 grams or 34 percent of the theoreticalyield. The polymer had a specific viscosity, determined on 0.5 percentsolutions in percent formic acid, of 1.348.

EXAMPLE VI To 0.5 gram samples of each, an antimony pentachlorideactivated polypyrroiidone and a benzoyl chloride activatedpolypyrrolidone prepared from the same batch of monomer and inaccordance with the procedure of Example 111, there was added 5.0 ml. ofan aqueous solution of an acid dyestuff, Calcocid Alizarin 121 Blue SATXC. LAcid Blue 45; C. I. No. 63010 (in a concentration of 0.53 gram perliter of water). There was also added to the samples ml. of water and0.2 ml. of glacial acetic acid. Each mixture was boiled vigorously forseconds, then filtered and the polymer washed with water. The benzoylchloride activated sample only partially exhausted the dye from the dyebath, whereas the antimony pentachloride activated polypyrrolidonealmost completely exhausted the dye from the dye bath. The depth of thedye on the antimony pentachloride activated polypyrrolidone was easilyperceptible to the eye to be much greater than that of the benzoylchloride activated polymer.

The dyed polymers were then separately put into ml. of water and to eachmixture there was added 0.5 ml. of concentrated ammonium hydroxide. Eachmixture was boiled vigorously for 15 seconds and again filtered. Theantimony pentachloride activated polypyrrolidone remained deeply dyed,whereas the benzoyl chloride activated polymer was Weakly dyed.

The new activators of the present invention present many advantages overthose known in the prior art. For example, polypyrrolidone prepared inthe presence of these new activators has a greatly increased specificviscosity as well as good color. Further-more, extremely good yields ofpolymer are obtained in polymerization procedures where the newactivators are used. Another distinct advantage exhibited by the newactivators of this invention is the greatly increased dyea-bility ofpolypyrrolidone prepared from polymenizations in which they areutilized. At the same time that the new activators of this inventionresult in the formation of polypyrrol-idone which has greatly improvedproperties, the other physical characteristics of the polymer, such assolubility, for example, are not affected. In addition, the use of thenew activators disclosed herein decreases materially the amount of timenecessary to carry a pyrrolidone polymerization to completion. The newactivator compounds are also readily available and inexpensive and maybe employed without substantial changes in existing equipment used forpyrrolidone polymerization. Numerous other advantages will be apparentto those skilled in the art.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that the same is not to be limited to the specificembodiments thereof except as defined in the appended claims.

We claim:

1. A process for polymerizing pyrrolidone which comprises forming underessentially anhydrous conditions a mixture containing monomericpyrrolidone, a catalyst selected from the group consisting of alkalimetals, pyrrolidone salts of alkali metals, hydrides of a lzali metalsand alkali metal alkyls and aryls, and a polymerization activatorselected from the group consisting of the trihalides of aluminum,bismuth and antimony, the tetrahalides of tin, titanium, zirconium andlead, and the pentahalide of antimony, said catalyst being employed in arange of 0.002 to 0.25 chemical equivalents of catalyst, said chemicalequivalents being based upon the gram molecular weight of. said catalystdivided by the valence of the metal in the catalyst based upon one moleof monomeric pyrrolidone, and said activator being employed in a rangeof 0.0001 to 0.075 chemical equivalents of activator, said chemicalequivalents being based upon the gram molecular weight of the activatordivided by the number of halogen atoms in the activator based upon onemole of monomeric pyrrolidone with a slight excess of catalyst overactivator being present in said mixture, and subjecting said mixture toa temperature in a range of 70 C. to 100 C.

2. The process as defined in claim 1 wherein the catalyst is sodiumhydride.

3. The process as defined in claim 1 wherein the catalyst is potassiumpyrrolidone.

4. The process as defined in claim 1 wherein the catalyst is sodiumpyrrolidone,

5. The process as defined in claim 1 wherein the catalyst is sodiumphenyl.

6. The process as defined in claim 1 wherein the polymerizationactivator is stannic chloride.

7. The process as defined in claim ll wherein the polymerizationactivator is aluminum trichloride.

3. The process as defined in claim ll wherein the polymerizationactivator is antimony pentachloride.

9. The process as defined in claim ll wherein the polymerizationactivator is titanium tetrachloride.

10. The process as defined in claim 1 wherein the polymerizationactivator is bismuth trichloride.

11. A process for polymerizing pyrrolidone which comprises forming underessentially anhydrous conditions a mixture containing monomericpyrrolidone, a catalyst selected from the group consisting of alkalimetals, pyrrolidone salts of alkali metals, hydrides of alkali metalsand alkali metal alkyls and aryls, and a polymerization activatorselected from the group consisting of the trihalides of aluminum,bismuth and antimony, the tetrahalides of tin, titanium, zirconium andlead, and the pentahalide of antimony, said catalyst being employed in arange of 0.005 to 0.25 chemical equivalents of catalyst, said chemicalequivalents of the catalyst being based upon the gram molecular weightof said catalyst divided by the valence of the metal in said catalystbased upon one mole of monomeric pyrrolidone, and said activator beingemployed in a range of 0.001 to 0.075 chemical equivalents of activator,said chemical equivalents of activator being based upon the grammolecular weight of said activator divided by the number of halogenatoms in said activator based upon one mole of monomeric pyrrolidonewith a slight excess of catalyst over activator bemg present in saidmixture, and subjecting said mixture to a temperature in the range of 20C. to 70 C.

12. The process as defined in claim 11 wherein the polymerizationcatalyst is sodium hydride.

13. The process as defined in claim 11 wherein the polymerizationcatalyst is potassium pyrrolidone.

14. The process as defined in claim 11 wherein the polymerizationactivator is stannic chloride.

15. The process as defined in claim 11 wherein the polymerizationactivator is antimony pentachloride.

1d. The process as defined in claim 11 wherein the polymerizationactivator is aluminum trichloride.

17. A process for polymerizing pyrrolidone which comprises forming amixture under essentially anhydrous conditions containing 0.294 mole ofmonomeric pyrrolidone, and 0.0315 chemical equivalents of potassiumhydroxide, said chemical equivalents being based upon the gram molecularweight of potassium hydroxide divided by the valence of potassium,reacting said mixture by subjecting the same to a temperature of 25 C.and removing the water which is formed during the reaction by vacuumdistillation, adding 0.0147 chemical equivalents of antimonypeutachloride, said chemical equivalents being based upon the grammolecular weight of antimony pentachloride divided by the number ofhalogen atoms in antimony pentachloride to the reaction mixture, andthereafter maintaining the reaction mixture at a temperature of 25 C.

18. A process for polymerizing pyrrolidone comprising forming underessentially anhydrous conditions a mixture containing.0.294 mole ofmonomeric pyrrolidone, 0.01192 chemical equivalents of stannic chloride,said chemical equivalents being based upon the gram molecular weight ofstannic chloride divided by the valence of stannic, and 0.0315 chemicalequivalents of sodium hydride, said chemical equivalents being basedupon the gram molecular weight of sodium hydride divided by the valenceof sodium and subjecting the mixture to a temperature of 25 C.

i). A process for preparing polypyrrolidone which comprises polymerizingpyrrolidone under substantially anhydrous conditions in the presence ofa catalytic amount 9 of an alkali metal salt of pyrrolidone as catalystand a promoting amount of a compound selected from the group consistingof aluminum bromide and aluminum chloride as activator and allowing thepyrroiidone to polymerize to a solid polymer.

20. A process for preparing polypyrrolidone which comprises polymerizingpyrrolidone under substantially anhydrous conditions in the presence ofa catalytic amount of an alkali metal salt of pyrrolidone as catalystand at promoting amount of a tetrahalide of a metal selected from thegroup consisting of lead, tin, titanium and zirconium as activator andallowing the pyrrolidone to polymerize to a solid polymer.

References Cited UNITED STATES PATENTS 2,622,076 12/1952 Koch 20782,739,959 3/1956 Ncy et a1. 260-78 2,806,841 9/1957 Barnes et al. 26078FOREIGN PATENTS 870,844 3/1942 France.

1() WILLIAM H. SHORT, Primary Examiner.

MILTON STERMAN, H. BURSTEIN, Examiners.

J. A. SKOLER, H. D. ANDERSON, Assistant Examiners.

1. A PROCESS FOR POLYMERIZING PYROLIDONE WHICH COMPRISES FORMING UNDERESSENTIALLY ANHYDROUS CONDITIONS A MIXTURE CONTAINING MONOMERICPYRROLDIDONE, A CATALYST SELECTED FROM THE GROUP CONSISTING OF ALKALIMETALS, PYRROLIDONE SALTS OF ALKALI METALS, HYDRIDES OF ALKALI METALSAND ALKALI METAL ALKYLS AND ARYLS, AND A POLYMERIZATION ACTIVATORSELECTED FROM THE GROUP CONSISTING OF THE TRIHALIDES OF ALUMINUM,BISMUTH AND ANTIMONY, THE TETRAHALIDES OF TIN, TITANIUM, ZIRCONIUM ANDLEAD, AND THE PENTAHALIDE OF ANTIMONY, SAID CATALYST BEING EMPLOYED IN ARANGE OF 0.002 TO 0.25 CHEMICAL EQUIVALENTS OF CATALYST, SAID CHEMICALEQUIVALENTS BEING BASED UPON THE GRAM MOLECULAR WEIGHT OF SAID CATALYSTDIVIDED BY THE VALENCE OF THE METAL IN THE CATALYST BASED UPON ONE MOLEOF MONOMERIC PYRROLIDONE, AND SAID ACTIVATOR BEING EMPLOYED IN A RANGEOF 0.0001 TO 0.075 CHEMICAL EQUIVALENTS OF ACTIVATOR, SAID CHEMICALEQUIVALENTS BEING BASED UPON THE GRAM MOLECUALR WEIGHT OF THE ACTIVATORDIVIDED BY THE NUMBER OF HALOGEN ATOMS IN THE ACTIVATOR BASED UPON ONEMOLE OF MONOMERIC PYRROLIDONE WITH A SLIGHT EXCESS OF CATALYST OVERACTIVATOR BEING PRESENT IN SAID MIXTURE, AND SUBJECTING SAID MIXTURE TOA TEMPERATURE IN A RANGE OF -70*C. TO 100*C.